Trigonometry (11th Edition) Clone

Published by Pearson
ISBN 10: 978-0-13-421743-7
ISBN 13: 978-0-13421-743-7

Chapter 6 - Inverse Circular Functions and Trigonometric Equations - Section 6.1 Inverse Circular Functions - 6.1 Exercises - Page 264: 42



Work Step by Step

The value of $\theta$ must be in the interval $[0^o, 90^o) \cup (90^o, 180^o] $. $\theta=\sec^{-1}{(-2)}$ means that $\sec{\theta} = -2$. Since secant is the reciprocal of cosine, then $\sec{\theta} = -2$ means $\cos{\theta}=-0.5$ Note that $\cos{120^o} = -0.5$. Thus, $\sec^{-1}{\left(-2\right)}=120^o$
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